1. Field of the Invention
The present invention relates to a biosensor and a method of driving the same, and more particularly to a biosensor in which a reference electrode and a fluid line are implemented in one body to enable miniaturization and a method of driving the same.
2. Discussion of Related Art
Among biosensors detecting biomolecules using an electrical signal, a transistor-based biosensor including a transistor has high electrical signal conversion speed and can be manufactured as an integrated circuit (IC). Thus, research on the transistor-based biosensor is actively under way.
FIG. 1 illustrates a conventional biosensor measuring a biological reaction using a field effect transistor (FET).
Referring to FIG. 1, in the conventional FET-based biosensor, a source and a drain 110 are formed on a substrate 100, and a channel 115 is formed between the source and drain 110.
A gate insulating layer 120 is formed on the channel 115, and a probe molecule layer 160 is formed on the gate insulating layer 120.
Meanwhile, source and drain electrodes 140 connected with the source and drain 110 are formed on an insulating layer 130, and an isolation layer 150 is formed on the source and drain electrodes 140.
As described above, the probe molecule layer 160 on the gate insulating layer 120 is exposed to the outside, and a sample solution 180 flows on the probe molecule layer 160.
Here, a reference electrode 190 for applying a gate voltage VGate of a FET is dipped in the sample solution 180, and the gate voltage VGate is transferred to the sample solution 180 by the reference electrode 190. A difference in electric potential between the reference electrode 190 and the sample solution 180 is kept uniform.
When target molecules 170 in the sample solution 180 are combined with probe molecules of the probe molecule layer 160 on the gate insulating layer 120, the electric potential of the surface of the gate insulating layer 120 is changed by electric charges that the target molecules 170 have. Thus, the value of a threshold voltage for applying current to the channel 115 under the gate insulating layer 120 is changed.
By reading the change in the threshold voltage of the FET, it is detected whether or not a reaction occurs. At this time, the reliability of the threshold voltage deteriorates unless the difference in electric potential between the reference electrode 190 and the sample solution 180 is kept uniform.
Also, since the reference electrode 190 must be dipped in the sample solution 180, it is difficult to reduce the size of the biosensor even if the FET is miniaturized. Consequently, there is a limit in increasing the sensitivity of the biosensor and reducing the measurement time.